Alice Wells, the principal deputy assistant secretary for the State Department's Bureau of South and Central Asian Affairs, told reporters she had been struck by Ghani's proposal.

"I heard him offering a dignified process," she said.

"This is not a surrender that's being offered to the Taliban, but a dignified process for reaching a political framework," she added, noting that the Kabul conference was "really a historic benchmark event."

Wells said the Afghan government had "listened carefully" to the Taliban and was responsive to a number of their requests.

Ghani's offer was "quite forward-leaning and frankly I think probably caught the Taliban by surprise," Wells said. "This was quite a courageous offer."

"We certainly encourage the Taliban to take this offer seriously. It does put the onus on the Taliban to respond," she added.

Last week, the Taliban said it was prepared to enter direct talks with the US to find a "peaceful solution" to more than 16 years of war.

That statement however made no mention of negotiating with the Afghan government -- a condition which the US has long stated is vital to any peace process.